Firefighters are still battling huge wildfires that forced mass evacuations of some 80,000 people earlier this week in Alberta, Canada.

Police and military officers are leading a convoy of about 500 vehicles through wreckage out of the oil sands camps where they had been staying since Tuesday. As many as 8,000 people were airlifted to safety Thursday, 5,500 more were expected to be flown out Friday, and another 4,000 were expected to be airlifted Saturday.

More than 80,000 people have fled Fort McMurray in the heart of Canada's oil sands, where the fire has destroyed 1,600 buildings.

The Alberta provincial government, which declared a state of emergency, said Friday that the size of the fire had grown to more than 101,000 hectares.

So far, investigators have not figured out what sparked the wildfires that erupted Sunday. Officials said the fire started in a remote forested area and could have been ignited by lightning.

Unseasonably hot temperatures combined with dry conditions have transformed the boreal forest in much of Alberta into a tinder box.